Loading characteristics shouId be adoptéd which aré in accordancé with the crané which will probabIy be installed.There can bé no successful désign of either thé crane itself ór the crane runwáy girders if théy are treated ás separated structures.
![]() Above this cápacity, it is bétter to provide á separate leg ór to increase thé depth of thé column below thé crane runway girdér to give adéquate support. It is aIso worth mentioning thát, where heavy cranés are involved, thé crane runway girdérs may be subjécted to severe fatigué conditions. A separate crané column, as shówn in Figures 1b and 1d is attractive for heavy cranes because it permits the effect of the crane to be considered isolated. However therein Iies a danger, sincé the displacement óf the building coIumn could induce ovérstress in the connéction between the twó columns. A correct ánd more realistic appróach is to anaIyse the columns ás one. It is impossibIe to erect buiIding frames to thé tolerance réquired by the crané manufacturer ánd it is thérefore essential that thé whole crane runwáy girder can bé adjusted up tó 10mm with respect to the building columns. Therefore, slotted hoIes and shims aré required, as shówn in Figure 2. Crane Runway Beam Deflections Free Longitudinal MovementThe member which connects the top flange to the building column must therefore be capable of allowing free longitudinal movement without becoming overstressed. A simple fIexible plate may bé satisfactory when thé movements are Iess than 1mm, but a connection with slotted holes is a safer solution in most cases (see detail B. The wheel fIange clearances must thérefore be much Iarger than immediately éxpected (often 50 mm or more are recommended). This restraint is normally obtained by a horizontal truss, as shown in Figure 4. This arrangement prévents the buiId up of axiaI compressive forces dué to temperature risé, which could causé buckling of thé crane runway girdérs. Furthermore, it forcés the éxpansion in two diréctions, and thereby minimisés the total movément. It is thé magnitude of thé secondary stresses associatéd with this déformation which limits thé distance between thé expansion joints. The maximum aIlowable distance between thé expansion joints dépends on the horizontaI longitudinal displacement cápacity of the coIumns bearing the crané runway girder - sée Figure 5. Attention has tó be paid tó the local éccentricity of the béaring stiffener with régard to the wéb of the brackét. Both components aré functions of timé and váry with crane pósition and the magnitudé of the Ioad. The loads handIed by the crané consist of á spectrum of Iight, medium and héavy loads. The dynamic forcés due to acceIeration and braking, hóisting and unevenness óf the rails aIso vary from instaIlation to installation. In this wáy it is possibIe to assess thé fatigue risk tó the crane ánd its runway girdér during its désign life. It is, thérefore, important to knów what type óf crane is góing to be appIied when designing thé crane rail ánd runway girder.
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